Optical character recognition systems, or optical scanners, have become increasingly useful for reading data in a wide variety of applications. Optical character recognition systems are used to sort the large volumes of incoming mail received by banks, credit institutions, taxing authorities, postal services, and department stores and to store information from other documents, in digital form, in a memory device.
Recent developments in data handling have further emphasized the need to quickly and accurately identify coded data, such as bar code patterns for purposes of location, sortation or routing. Bar codes have become a popular method of manifesting coded information for sorting large volumes of materials. For example, with the ever-increasing volume of letter mail, there is a need for a rapid, accurate identification of bar code patterns in which address information is encoded by the height of equally-spaced bars of equal width for mechanical sorting to ensure rapid and accurate mail deliveries. The transport velocities of this mail is often very high, usually between 100 and 200 inches per second. Similarly, document identification and sortation is also a significant problem in many industries such as banking and insurance, where a significant volume of paperwork must be processed daily on a reliable basis.
The rapid identification of bar codes is often impeded by certain adverse conditions. In applications, for example, where coded information is utilized to sort returnable media, and in the warehousing industry, the data code manifestations are subject to rough usage and parts thereof are distorted if not destroyed. The surface on which the manifestation of the coded data may appear may be distorted or cause the manifestation to be distorted. Furthermore, as with letter mail, the data code manifestations are subject to being over-written or otherwise marked over. The very rapid speeds at which the bar code must be located, interpreted, validated as to its proper format, corrected when errors are identified and, when multiple valid codes appear, the appropriate code selected magnifies the effects of these adverse conditions. As compared to bar codes such as the Uniform Product Code in which the information is coded by the width or thickness of the bar, bar codes in which information is encoded according to the height of equally spaced bars of equal width require much more computation and, therefore, time to locate and recognize. At very high transport velocities of the surface of the object imprinted with bar code patterns in which bars vary in height, a system is required to provide for quick and reliable location and recognition of bar codes with a minimum amount of computation, and therefore minimum time and cost, in the presence of the adverse conditions outlined above. In particular, the United States Postal Service has proposed and uses bar codes having full bars and half bars as set forth in Address Block Bar Code, United States Postal Service Development Specification dated Sept., 1987. There is, therefore, a specific need for a bar code identification and recognition system to locate and read reliably over 95% of the POSTNET bar codes on mail, as required by the United States Postal Service, at letter transport speeds of between 100 and 200 inches per second. More generally, there is a need for an optical character recognition system that is capable of reliably locating and reading bar code data on the surfaces of objects, or other types of surface manifestations at very high rates and velocities, possibly with physical distortions and with the bar code partially obscured by over-writings and stray marks.